What resolution do you play at? What brand/wattage is your power supply? The best upgrade would be the GFX card (most games aren't coded for more than 2 cores anyway). Do you have a 64bit OS? If so another cheap upgrade would be more RAM.
Thanks for all the quick replies. I an running a 64 bit os and i play at 1080p, i do not like to go lower with the res.
my psu is an ocz stealth x stream 650 watt.
i was also thinking of getting 4 more gigs of ram since it would only cost 25 bucks on newegg.
i suppose a gfx card is wat ill upgrade. I'm thinking of getting the radeon hd 6870
what do you think about this choice? it also comes with deus ex free =] http://www.newegg.com/Product/Product.aspx?Item=N82E168...